The present invention is in the field of xe2x80x9cflat-proofingxe2x80x9d pneumatic tires. Since its invention in 1845 to the present day, the pneumatic tire has only one fundamental problem. The loss of compressed air from inside the tire while in use. If the pneumatic tire is punctured, the entire volume of compressed air inside the tire is lost and the tire goes flat. If just a small portion of the pneumatic tire""s structure fails, the entire volume of compressed air inside the tire is lost and the tire goes flat.
This fundamental problem was evident during the summer of 2000 when a tire blow-out problem gained national attention. The National Highway Traffic Safety Administration subsequently announced a total of 271 people who died as a direct result of tire blow-outs, continuing to illustrate the ongoing danger of suddenly losing the air pressure from inside a tire at highway speeds.
The danger of flat tires reaches to both ends of the driving spectrum. Whether you are going 200 mph on a racetrack or you are going 0 mph, caught having to change a flat tire in the wrong place at the wrong time. Indy driver Scott Brayton was killed in 1996 when his right rear tire suddenly went flat while going 230+ mph during practice for the Indy 500. Ennis Cosby was killed in 1997 while changing a flat tire on a dark stretch of road in Los Angeles.
At the present time, other than liquid tire sealants which function essentially the same way, the only commercially available xe2x80x9cflat-proofingxe2x80x9d means for use on public highways is a tire having a layer of sealant molded into the tread portion of the tire. The sealant layer seals xe2x80x9croundxe2x80x9d holes up to approximately xc2xc of an inch in diameter in the tread only. If a puncture is sustained in the sidewall, the tire will go flat because there is no sealant layer in the sidewalls; if a straight xe2x80x9ccutxe2x80x9d is made through the tread, the tire will also go flat because the sealant layer will only seal round holes This sealant layer technology goes back about sixty years and really only addresses small nails and related things puncturing the tread. Even without a sealant layer, most nails in the tread of a regular tire just produce a slow leak, not a dangerous blow-out situation. Therefore the sealant technology, which is the only thing currently available for highway use, does not solve the real flat tire problem.
The run-flat tire technology allows run-flat tires to be driven up to fifty miles at reduced speed after the entire volume of compressed air inside the tire is lost due to a puncture. But run-flat technology is limited to tires with low aspect ratios, i.e. small sidewalls. The aspect ratio is the sidewall height divided by the maximum section width.
One approach to achieving a truly xe2x80x9cblow-out proofxe2x80x9d and xe2x80x9cflat-proofxe2x80x9d tire is to completely fill the interior of the tire with an elastomeric cellular structure comprised of individual, pressurized closed cells. Applicant""s approach is to use the composite cellular structure described in Applicant""s U.S. Pat. Nos. 5,031,679 and 5,080,737. The composite cellular structure, or xe2x80x9cSyntactic Foam Tire Insertsxe2x80x9d, described therein, can be made in two different configurations. A complete fill tire insert and a tire xe2x80x9clinerxe2x80x9d insert. The complete fill tire insert completely fills the interior of a pneumatic tire, with all of the required air pressure captured in a multiplicity of individual pressurized cells. Thus making a pneumatic tire blow-out proof and flat-proof, because the entire volume of compressed air inside the tire can never be lost due to a puncture, or if a portion of the tire fails. While this would seem to be the answer, there are some problems with implementing a complete fill tire insert. The main problem is that a tire that has its interior completely filled with a xe2x80x9ctire insertxe2x80x9d can not be mounted onto a one-piece drop center wheel. The type of wheel used on all vehicles. In mounting a tire onto a one-piece drop center wheel, a portion of the bead of the deflated tire is first forced into the xe2x80x9cdrop centerxe2x80x9d portion of the wheel. This allows the bead to assume an oval shape and slip over the wheel. Trying to mount a tire that has its interior completely filled with a cellular structure that has xe2x80x9cpressurizedxe2x80x9d cells, would be like trying to mount a tire that is already inflated. Try forcing the bead of an inflated tire into the drop center portion of the wheel. Clearly not possible by any practical means. The complete fill tire insert requires a two-piece bolt together wheel. The two-piece bolt together wheel that would be required is shown in FIG. 7. As two-piece wheel 35 in FIG. 7 shows, the two individual halves of the wheel can simply be placed in the tire and bolted together. However, except for some heavy equipment vehicles and the civilian version of the military""s HMMWV, no vehicle comes equipped with two-piece bolt together wheels. No manufacturer makes two-piece bolt together wheels to replace the one-piece drop center wheels that come on virtually all vehicles.
The tire xe2x80x9cLinerxe2x80x9d configuration solves the tire mounting and two-piece wheel problem of the complete fill tire insert. The xe2x80x9cLinerxe2x80x9d, lines the interior surface of the tire with a given thickness, providing a void in the center of the tire for a subsequently pressurized air chamber. The Liner and pressurized Air Chamber function together as a system that establishes the entire load bealing capability of the tire. Because the tire liner insert does not completely fill the interior of the tire, a tire equipped with a xe2x80x9cLinerxe2x80x9d can be mounted onto existing one-piece Original Equipment Manufactured (O.E.M.) wheels. And while the complete fill tire insert allows for punctures all the way to the wheel, this capability is really unnecessary. As almost all tire punctures encountered during driving, penetrate the tire maybe a couple of inches. Therefore the Liner and Air Chamber System will make a tire blow-out proof and flat-proof. And in the event a puncture does penetrate all the way through the Liner and depressurizes the air chamber, the Liner itself provides sufficient load bearing capability to allow the vehicle to be driven to a safe location to change the tire. Depressurizing the air chamber is the equivalent of releasing that same volume of compressed air out of a regular tire. The tire would be xe2x80x9clowxe2x80x9d, but it still could be driven to a safe location.
The Liner now would seem to be the answer, but there is a problem with the tire liners of the prior art. FIG. 6 shows an example of the tire liners of the prior art 90, lining a tire with a high aspect ratio, i.e. large sidewalls. Tires with high aspect ratios have greater sidewall displacement for the same percentage of load deflection, than low aspect ratio tires. The prior art liners 90 may work in tires with low aspect ratios. Low aspect ratio tires have small sidewalls and therefore substantially less sidewall displacement under a load. Which is why run-flat tires are low aspect ratio tires only. But if the prior art liner 90 is used in a tire with large sidewalls, there is a problem. Large cars, trucks, SUVs, etc., are all vehicles that utilize large sidewall, high aspect ratio tires. And are all vehicles where run-flat technology will not work. As FIG. 6 shows, in the cross section that is parallel with the rotational axis of the tire, the tire liners of the prior art 90, line this cross section with one structure of uniform thickness. When prior art liner 90 encounters xe2x80x9chigh tire deflectionsxe2x80x9d during use, an extreme tension load is placed on areas 73, where the sidewall portion is connected to the tread portion. In the May 4, 1998 issue of Design News magazine, page 80, an article on run-flat tires points out the problem of extreme tension for tires running while flat. A localized extreme tension load causes the same problem for a xe2x80x9ctire linerxe2x80x9d as it does for a tire. So as the large sidewalls of the high aspect ratio tire deflect under load 70, areas 73 are stretched. This is due in part to pressurized air chamber 93 which pushes on prior art liner 90 and keeps liner 90 in contact with the interior surface of the tire at all times. The reason the entire tread portion of prior art liner 90 does not seem to be under a detrimental tension load, is because air pressure force 97 tends to xe2x80x9cclampxe2x80x9d the tread portion to the inside surface of the tire and keep it from moving. The air pressure force 97 that pushes on the tread portion of prior art liner 90 is at a right angle to load deflection 70. This is the problem with using prior art liner 90 in a high aspect ratio tire/high deflection application. Because these two lines of force are ninety degrees (90xc2x0) to each other, the areas where the sidewall portions are connected to the tread portion 73 have to go into tension during load deflection 70. The more the tire deflects under load, the more extreme the tension load that is placed on areas 73. This cyclical extreme tension load, going from a neutral load (no deflection), to an extreme tension load (deflection), back to a neutral load (no deflection) as a high aspect ratio tire with prior art liner 90 is put to use, generates so much heat that areas 73 actually melt, causing prior art liner 90 to fail.
High tire deflections can not result in extreme tension loads being placed on a tire liner. A tire liner for a high aspect ratio tire should be under a compression load only.
The object of the present invention is to provide a functional means of eliminating pneumatic tire blow-outs and flats for high aspect ratio tires/high deflection applications, that can be utilized with existing one-piece drop center wheels.
The present invention is a system incorporating a cellular tire xe2x80x9cLinerxe2x80x9d, thereby solving the tire mounting and two-piece wheel problem, and an Air Chamber. The present invention Cellular Tire Liner and Air Chamber System provides an air chamber that is essentially vee shaped, which eliminates right angle forces on the sidewalls and tread portion of the Liner and eliminates the localized extreme tension loads. The present invention Cellular Tire Liner and Air Chamber System provides an annular interface which disconnects the sidewall portions from each other, further eliminating extreme tension loads during high tire deflections.